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Evidence for distal transport of reworked Andean tephra: extending the cryptotephra framework from the Austral volcanic zone

Evidence for distal transport of reworked Andean tephra: extending the cryptotephra framework from the Austral volcanic zone
Evidence for distal transport of reworked Andean tephra: extending the cryptotephra framework from the Austral volcanic zone

Cryptotephra deposits (non-visible volcanic ash beds) may extend thousands of kilometres and provide valuable chronological isochrons. Here, we present a Lateglacial-early Holocene (c. 16,500 cal yr BP-6000 cal yr BP) tephrostratigraphy from Hooker's Point, East Falkland, South Atlantic. This period spans the last glacial termination across the southern mid-latitudes, a time period during which the palaeoenvironmental record is poorly resolved in southern South America and the South Atlantic. The development of a regional tephrostratigraphy will provide chronological constraint for palaeoenvironmental records from this period. Two cryptotephra deposits from Hooker's Point are linked with Mt. Burney, including the early-Holocene MB 1 tephra, while a third is likely to be derived from the R 1 eruption of Reclus volcano. The high shard abundance of these cryptotephra deposits suggests they extend further into the Southern Ocean, and may act as regional stratigraphic markers during the Lateglacial. Further peaks in shard abundance are composed of detrital glass (tephra not derived from primary air fall events), with mixed shard morphologies and geochemically heterogeneous glass populations. This detrital glass is likely to have been repeatedly reworked by wind action in the Patagonian Steppe before final deposition in the Falkland Islands. The high abundance of detrital glass in the Hooker's Point sequence suggests long distance transport of reworked tephra is common in this region, and highlights the need to carefully analyse cryptotephra deposits in order to avoid incorrectly describing reworked tephra as new isochrons. A temporal pattern of shard abundance is apparent in the Hooker's Point sequence with a reduction/absence of shards between 14,300–10,500 cal yr BP.

Austral volcanic zone, Cryptotephra, Falkland Islands, Reworking, Tephrochronology
1871-1014
64-71
Monteath, A.J.
51195e1e-5ac5-4845-a4fc-e9f86862a2db
Hughes, P.D.M.
14f83168-b203-4a91-a850-8c48535dc31b
Wastegård, S.
5c01a086-db18-4d4c-aa23-8679edd2b86b
Monteath, A.J.
51195e1e-5ac5-4845-a4fc-e9f86862a2db
Hughes, P.D.M.
14f83168-b203-4a91-a850-8c48535dc31b
Wastegård, S.
5c01a086-db18-4d4c-aa23-8679edd2b86b

Monteath, A.J., Hughes, P.D.M. and Wastegård, S. (2019) Evidence for distal transport of reworked Andean tephra: extending the cryptotephra framework from the Austral volcanic zone. Quaternary Geochronology, 51, 64-71. (doi:10.1016/j.quageo.2019.01.003).

Record type: Article

Abstract

Cryptotephra deposits (non-visible volcanic ash beds) may extend thousands of kilometres and provide valuable chronological isochrons. Here, we present a Lateglacial-early Holocene (c. 16,500 cal yr BP-6000 cal yr BP) tephrostratigraphy from Hooker's Point, East Falkland, South Atlantic. This period spans the last glacial termination across the southern mid-latitudes, a time period during which the palaeoenvironmental record is poorly resolved in southern South America and the South Atlantic. The development of a regional tephrostratigraphy will provide chronological constraint for palaeoenvironmental records from this period. Two cryptotephra deposits from Hooker's Point are linked with Mt. Burney, including the early-Holocene MB 1 tephra, while a third is likely to be derived from the R 1 eruption of Reclus volcano. The high shard abundance of these cryptotephra deposits suggests they extend further into the Southern Ocean, and may act as regional stratigraphic markers during the Lateglacial. Further peaks in shard abundance are composed of detrital glass (tephra not derived from primary air fall events), with mixed shard morphologies and geochemically heterogeneous glass populations. This detrital glass is likely to have been repeatedly reworked by wind action in the Patagonian Steppe before final deposition in the Falkland Islands. The high abundance of detrital glass in the Hooker's Point sequence suggests long distance transport of reworked tephra is common in this region, and highlights the need to carefully analyse cryptotephra deposits in order to avoid incorrectly describing reworked tephra as new isochrons. A temporal pattern of shard abundance is apparent in the Hooker's Point sequence with a reduction/absence of shards between 14,300–10,500 cal yr BP.

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Falkland_s_tephra_Manuscript_Final_ - Accepted Manuscript
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More information

Accepted/In Press date: 17 January 2019
e-pub ahead of print date: 18 January 2019
Published date: 1 April 2019
Keywords: Austral volcanic zone, Cryptotephra, Falkland Islands, Reworking, Tephrochronology

Identifiers

Local EPrints ID: 429210
URI: http://eprints.soton.ac.uk/id/eprint/429210
ISSN: 1871-1014
PURE UUID: 643622b7-ae3c-435c-9625-d4e31ebacfc0
ORCID for P.D.M. Hughes: ORCID iD orcid.org/0000-0002-8447-382X

Catalogue record

Date deposited: 22 Mar 2019 17:30
Last modified: 26 Nov 2021 05:22

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Contributors

Author: A.J. Monteath
Author: P.D.M. Hughes ORCID iD
Author: S. Wastegård

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